The invention relates to a compact heat exchange device of low cost, for use in heat exchanges involving several fluids, such as gases.
The exchange surface, per volume unit, of the tube-and-sheet exchangers, which are frequently used, is limited by the difficulty of reducing the diameter of the tubes and the distance between the tubes below a value of about 1 cm.
The plate exchangers provide larger specific exchange surfaces. In these exchangers, the fluids taking part in the exchange circulate on both sides of the plates, but the specific surface is also limited by the need to maintain a sufficient distance between the plates.
It has already been proposed to build a compact exchanger at low cost by stacking perforated plates so as to obtain channels, by superposition of the perforations, through some of which is passed one of the fluids taking part to the exchange while another fluid taking part in the exchange is passed through others, and with the heat being transferred between the fluids circulating in the channels by conduction through the material forming at least one part of said plates. The plates are then preferably made of a metallic material having good heat conductivity.
An embodiment of this type is described in U.S. patent application Ser. No. 145,651 filed on the May 2, 1980, now U.S. Pat. No. 4,368,779 issued Jan. 18, 1983, and assigned to the same Assignee as the instant application. It is illustrated by FIGS. 1A and 1B of the accompanying drawings.
In this device, the heat exchange takes place between a fluid A, and a fluid B at a different temperature from A, which pass through distinct groups of channels, for example, according to the arrangement of FIG. 1B (showing, in cross-section, the plates stacking), in such manner that each channel wherethrough is passed one of the fluids is adjacent to at least one channel wherethrough is passed the other fluid. The channels are designated by the arrows 2a to 2g of FIG. 1A, showing, a cross-section, of the exchanger along the plane A--A of the FIG. 1B.
This arrangement has the advantage of permitting a counter-current heat exchange between fluids A and B. However the problem is posed of supplying each of the fluids to each end of the apparatus. It is then necessary to provide each end of the device with at least one distributing plate comprising grooves overlapping the channels wherein circulates the fluid which is fed or discharged through said grooves. It is accordingly difficult to solve the problems relating to the construction of the units and to pressure drops, when distributing a gaseous fluid. In that case, as a matter of fact, in order to limit the pressure drop, the inlet and oulet cross-sectional areas must be approximately the same as the passage section used for the exchange.